Method for the production of titanium tetrachloride and zirconium chlorides



United States Patent 3,156,527 METHOD FOR THE PRODUQTEGN 0F TITA- NIUM TETRACHLGRIDE AND ZIRCONI- UM CHLGRIDES Arthur Wallace Evans, Nunthorpe, Middlesbrough, and

James Dennis Groves, Stockton-on-Tees, England, assignors to British Titan Products Company Limited, York, England, a corporation of Great Britain No Drawing. Filed Aug. 7, 1958, Ser. No. 753,616 5 Claims. (Cl. 2387) This invention deals with the treatment of zirconium bearing materials, particularly zircon and zirconium oxide and like zirconium oxide bearing materials which contain at least percent by Weight of ZrO and particularly to the use of such materials in connection with the production of titanium tetrachloride.

The chlorination of zircon and like zirconium oxide bearing materials takes place so slowly that dificulty is encountered in maintaining the temperature of reaction by the heat evolved therefrom.

According to this invention, it has been found that zirconium oxide bearing compositions containing at least 10 percent by Weight of ZrO either as such or in chemical combination, such as zircon or zirconium oxide itself, may be effectively chlorinated by simultaneously chlorinating a titanium bearing material, such as rutile, ilmenite or like titanium oxide bearing material, in the presence of a carbonaceous reducing agent, such as carbon or carbon monoxide, and using the exothermic heat evolved by the titanium chlorination to maintain the temperature of clflorination of the zirconium material. This may be accomplished, for example, by adding titanium oxide bearing material and carbon to a bed of zircon and carbon while fluidizing the bed in an upwardly rising stream of chlorine.

The temperature of chlorination should be above about 600 to 700 C. Where chlorination of zircon is to be achieved, the temperature of chlorination normally is held above about 925 to 950 C., rarely above 1400 C. Chlorination of the isolated oxide itself, ZrO may be conducted at a lower temperature.

According to a further embodiment of the invention, an improved method has been provided for chlorinating titanium bearing materials, such as titanium oxide hearing materials (rutile, ilmenite, Sorel slag, and the like). This chlorination is conducted by suspending the material to be chlorinated in an upwardly rising stream of the chlorinating gas, i.e., the material is suspended to provide a dynamic fluidized or dancing bed which is chlorinated by the upwardly flowing gaseous chlorination agent. We have found that it is necessary to conduct such a process under conditions such that the heat evolved during the chlorination maintains the bed at chlorination temperature (above 600700 C.). This requires establishment of a bed which retains appreciable heat so that the bed is not cooled unduly during addition of reactants or withdrawal of reaction products. Particularly is this true when the material undergoing chlorination is added to the bed at a temperature below that of chlorination, for example, below that at which the chlorination will support itself (below about 500 C.). The bed must not agglomerate or otherwise adversely affect the titanium chlorination.

According to this invention, titanium oxide bearing materials are effectively chlorinated in a dynamic (fluidized or dancing) bed, and the temperature of chlorination is eifectively maintained by establishing and maintaining in said bed a substantial amount of zircon. This zircon which is maintained in the bed retains a major portion of sensible heat in the bed and serves to dilute the incoming titanium oxide bearing material and transfer "ice heat thereto. As a consequence, it is possible to effect the desired reaction conveniently and Without preheating the ore to a temperature equal to or above the temperature of the reaction bed. Furthermore, when the ore contains certain components which tend to cause sintering or agglomeration of the bed particles as, for example, magnesium oxide or the like, the presence of the zircon in the bed may minimize this difficulty.

Where the ore itself contains an appreciable amount of zircon, an especially convenient method of establishing the zircon in concentration in the bed involves operation at temperature conditions such that zircon is not chlorinated. Thus, it has been found that by maintaining the temperature of the bed high enough to chlorinate the titanium components (usually above 700 C. but below about 950 C.), it is possible to build up and establish a substantial concentration of zircon in the bed since chlorination of the zirconium components of the ore undergoing introduction is substantially minimized.

In the practice of the operations herein contemplated, it is desired to make use of a bed containing about 10 to 55 percent by weight of Zr0 based on the total mineral content of the bed, i.e., computed on a carbon-free basis. However, the composition of the bed should not be allowed to fall below about 15 percent by weight of titanium dioxide (also on a carbon-free basis) at all events. The actual composition of the bed will depend to a large degree upon the concentration of titanium dioxide in the oxide bearing material fed to the bed. However, a good useful range of titanium dioxide content is from about 20 percent to about percent TiO by weight (also computed on a carbon-free basis). Silica is usually present in combination with the ZrO as zircon or coming as an impurity in the titanium ore. Moreover, other components, such as coke, may be present in the bed if desired or as an inevitable consequence of the composition of the material undergoing chlorination. The particle size of the zircon in the bed may range from 75 to 500 microns or may be smaller.

The process herein contemplated may be conducte effectively using the furnace described in copending application Serial No. 509,964, filed May 20, 1955, Which has now matured into US. Patent No. 2,855,273, granted October 7, 1958, the disclosure of which is incorporated herein by reference. 7

In the operation of the process, the furnace is brought up to temperature in any convenient way as, for example, by introducing a bed of coke or other carbonaceous mate 'rial, usually having a particle size of 200 to 250 microns or smaller, into the reaction zone of the furnace. The coke is ignited and air or oxygen is blown through the conduits to support combustion and to fluidize the coke. After the temperature of the furnace has raised to the desired level, usually above 500 C., and preferably 700 to 900 C., it is ready for commencement of the chlorination process.

To build up the zirconium content of the bed, a titanium ore or like material which contains zirconium is subjected to chlorination. This ore is mainly of the order of size 75 to 500 microns, with an average of to microns, and is mixed with powdered carbon, coke, anthracite or equivalent carbonaceous material with an average size of approximately 200 to 250 microns or below, but often having a wide scatter. The percentage of carbon to be added may vary according to other conditions such, for example, as the oxygen content of the chlorine gases fed in, but is usually from 10 to 50 percent by weight of the total ore. Normally, the orecarbon mixture is blended before feeding to the furnace although separate feeds for each constituent may be used.

arse,

To initiate the reaction, a quantity of the ore-carbon mixture is introduced into the furnace in amount sufficient to establish a bed about 1 to 6 feet in height. Chlorine is introduced into a reservoir below the reaction zone, with or without air or oxygen, and flows through suitable conduits into the bottom of the reaction zone at a rate sufiiciently high to establish a fluidized or dynamic bed.

The chlorination agent thus introduced chlorinates metal bearing components in the bed and thus titanium tetrachloride and iron chloride are formed and vaporized. As a consequence of the chlorination, heat is evolved, thus manitaining the temperature of reaction.

The reaction can be carried out continuously by feeding further chlorine, ore, and carbon continuously or intermittently to the bed and withdrawing the vapors from the bed. The temperature of the bed may be maintained at a convenient level by controlling the rate of chlorination. When the temperature is low, the rate of chlorine introduced is increased, and vice versa. Ore is introduced at a rate suflicient to maintain a bed at least one foot deep, measured when the bed is static, i.e., with the chlorine flow off.

The carbon is introduced at a rate suificient to maintain a substantial concentration of carbon in the reaction bed. For chlorination of rutile, the preferred concentration is approximately 20 percent by weight, based upon the weight of the ore. With other ores, the optimum concentration may be determined by laboratory experiments, as is understood in the art.

As explained above, it is advantageous to conduct chlorination of titanium bearing material in a bed which contains a substantial amount of zircon. This zircon may be introduced at the initiation of chlorination in order in order to establish a bed containing 10 to 55 percent ZrO based upon the total mineral content of the bed. Alternatively, the ZrO content of the bed may be generated by using an ore which contains zircon. By maintaining the temperature of the reaction bed below about 950 C. and by supplying as the ore undergoing chlorination a titanium bearing ore which contains a small amount of zircon, for example, 0.25 to 0.75 percent by weight of zirconium oxide, it is possible to gradually build up a bed which contains in excess of 10 percent by weight of zirconium oxide. If the tempera ture of the reaction mixture is maintained below 950 C. and the reaction using such an ore is carried out over a long period of time, the titanium dioxide content of the bed falls below to percent by weight. In such a case, chlorination becomes inefficient and thereupon it becomes important to remove a portion of zircon.

Removal of the zircon may be conducted by a number of methods. For example, the zircon may be removed by withdrawal of a portion of the bed through a suitable outlet and adding titanium oxide bearing material to replenish the bed.

According to a further embodiment, it is also possible to reduce the amount of zirconium in the bed by allowing the temperature to rise from time to time above 925 C., for example, 950 to 1150 C. or above (rarely above 1500 Q). As a consequence of such chlorination, the zirconium components chlorinate and can be reduced to any desired degree. Since the chlorination of zircon itself is comparatively slow, it is dilficult to maintain temperature of the reaction when zircon is chlorinated alone. Thus, the conjoint chlorination of both titanium and zirconium components at 925 C. or above, as achieved in this process, is advantageous since heat evolved by the titanium chlorination supports the zircon chlorination.

The following examples are illustrative:

EXAMPLE I The chlorination was conducted in a shaft furnace consisting of an outer steel shell lined with chlorine-resisting brickwork and having an internal diameter of 2 feet 6 inches. Near the base of the shaft furnace was a perforated plate, the perforations of which were fitted with orifices of restricted diameter and superimposed by ceramic gas-permeable barriers. The pressure drop acorss each of these orifices was 6 pounds per square inch. This plate comprises a refractory body, for example, jointed brickwork superimposed onto a steel base plate, the brickwork or a suitable cast refractory and base plate being formed with registering apertures each of which had an upper conical section at the top of which was inserted a disc of porous ceramic material, e.g., silica sand, cemented or lightly sintered. Beneath the base plate, apertured discs were attached to it and defined entrance orifices to the passages leading to the porous ceramic discs. These discs permitted the up-rising gases to enter the furnace but prevented dust or other solid material from passing down through the plate. Below the plate was a port through which chlorine gas was admitted. At the top of the shaft was provided a star valve through which a mixture of the titanium bearing material and carbon was admitted. Also, on one side of the furnace near the top was provided a port from which the gases leaving the fiuid bed were conveyed to the condensing system.

To commence the process, the chlorinator was filled with mineral rutile to a depth of 3 /2 feet and then fluidized by the admission of air and direct gas firing applied internaly to raise the temperature to 900 C. Carbon was then added to produce a bed containing 20 percent of carbon by weight.

Thereafter, chlorine was fed into the hot mass at a uniform rate of 400 pounds per hour to maintain a fluidized bed with a fluid gas velocity of about 18 centimeters per second at the operating temperature. The bed was maintained by feeding continuously through the star valve a mixture of mineral rutile and coke having the following analysis:

Table I Rutile Coke Percent Percent Particle Sizes M. 20-100 mesh (British Standard Mesh Size).

Table 11 Weight of Components in Bed in Kilograms Running Time, Days ZrO: SiOz Other era-5,527

During the first few days of operation there was an increase in the amount of certain components, mainly oxides of zirconium and silicon, in the bed. After further continuous operation, a state was reached in which the amount of such components present rose and fell, mainly due to lower or higher temperatures of operation within the range given above, but there was no build-up of impurity level above this approximately steady state. When these conditions were attained, it can be regarded that the ore feed was being completely chlorinated and the operation continued to the end of the 16 days run without any necessity to purge the bed.

EXAMPLE II The furnace used in this experiment had an internal diameter of 18 inches. The chlorine was introduced at the bottom to the distribution device of the type illls trated in FIGS. 1 and 2 of the drawing in the above mentioned application Serial No. 509,964, in which there were provided 21 gas ports each provided with orifices ,6 inch in diameter. The pressure drop across the gas distributor was approximately 6 pounds per square inch. The ore used was natural rutile having approximately the composition set forth in Example I.

Chlorination was initiated according to the method described in Example I, the amount of ore and carbon being introduced at a rate sufficient to establish a carbon cencentration of approximately 20 percent by weight, based upon the weight of the ore bed, and to introduce into the reactor enough ore such that the average height of the bed, when measured in static condition, normally was maintained at about 3.5 feet throughout the period of reaction. This operation was continued over a period of many days. The typical operation conditions were as follows:v

180 pounds per hour. 25 liters per minute.

6 pounds per square inch.

3 pounds per square inch.

50% rutile, 30%

20% carbon. 900 C.

zircon,

Temperature of the bed During the period of operation, approximately 2.35 tons of titanium tetrachloride was produced per day. The chlorine utilization exceeded 99 percent.

Addition of the ore was controlled so as to maintain the bed height in the range of 1.7 to 6.6 feet in depth, the depth being measured with the gas olf, that is, as a static bed. Once a shift, introduction of chlorine was discontinued for a few minutes in order to measure the static bed and to estimate the composition of the bed in terms of rutile and coke.

The ore which was fed had the following average particle size:

Percent by weight 44 to 76 microns 0.2 76 to 104 microns 3.9 104 to 124 microns 54.5 124 to 152 microns 30.2 152 to 188 microns 11.0 Greater than 188 microns 0.2

EXAMPLE III The process of Example II was performed while conducting the chlorination at a temperature of 900 C. while introducing chlorine at a rate of 180 pounds per hour. At the end of each 8-hour period, chlorine flow was temporarily discontinued and the bed was sampled and the depth thereof measured while static.

61 The following table sets forth the composition of the bed at various intervals:

Table III Weight in bed, Kilograms 'liO ZrO S102 Remainder After 1st day 39. 8 27. 3 15. 7 29. 2 After 14th day- 49. 6 42. 9 15. 5 13. 0 After 18th day- 43. 6 63. 4 37. O 8. 3

Thereafter, the bed temperature was raised to 950 C., whereupon the zirconium oxide concentration fell substantially. At the end of the 25th day, the bed had the following composition:

i.e., more zircon was being chlorinated at the higher temperature than was being added in the feed material.

The above examples illustrate the manner by which this invention may be performed using a titanium ore which inherently contains a small amount of zircon. It will be understood that the zircon can be obtained from other sources. Thus, zirconium tetrachloride and titanium tetrachloride may be produced simultaneously by adding a zircon ore or concentrate which contains above percent by weight of zircon to a bed undergoing chlorination while adding rutile or like titanium oxide bearing ore thereto concurrently, and maintaining the carbon content of the bed high enough to ensure chlorination, i.e., above about 12 percent by weight of the bed. As a general rule, the weight of zirconium (Zr) should not be over about three times the Weight of titanium (Ti) in the bed, nor should the TiO content of the bed fall below about 15 percent by weight (on a carbon-free basis) in order to ensure chlorination of titanium components and maintenance of temperature of reaction.

The following example is illustrative:

EXAMPLE IV The process of Example III is continued after the Zr0 content of the bed has been reduced to 57 kilograms by adding rutile at the same rate as before to hold the temperature at about 950 C. and adding enough zircon to hold the ratio ZrO to TiO in the bed substantially constant, the carbon concentration of the bed being held at about 20 percent by weight. Titanium tetrachloride and zirconium tetrachloride are formed and vaporized from the bed.

Although the various embodiments of the invention have been described with reference to specific details of certain features thereof, it is not intended that such details shall be regarded as limitations upon the scope of the invention except insofar as included in the accompanying claims.

This application is a continuation-in-part of applications Serial No. 469,062, filed November 15, 1954, now abandoned; and Serial No. 509,964, filed May 20, 1955, now United States Patent 2,855,273.

What is claimed:

1. A method of producing titanium tetrachloride by exothermic chlorination of titanium-bearing material containing titanium dioxide, which comprises establishng a fluid bed of particles containing titanium dioxide and zircon at 700 to 925 C. in a rising continuous gaseous stream comprising chlorine, which bed contains in excess of 15 percent by weight of titanium dioxide and about 10 to 55 percent by weight of zirconium oxide, based on the mineral content of the bed, providing in the bed sufficient amount of carbonaceous material to ensure formation and vaporization of titanium tetrachloride from the bed and periodically feeding particles containing titanium dioxide and zircon to said bed and continuing said chlorination until tle titanium dioxide content re duces toward said 15 percent by weight and in response to said reduction in titanium dioxide content, feeding enough of said titanium dioxide material to the bed to prevent the amount of titanium dioxide in said bed from falling below said 15 percent by weight and continuing chlorination to establish a zirconium oxide concentration of about said to 55 percent by weight.

2. A method of producing titanium tetrachloride and zirconium tetrachloride by exothermic chlorination of a fluid bed containing titanium dioxide-bearing and zirconbearing particles, which comprises establishing said bed at 700 to 925 C. in a rising continuous gaseous stream. comprising chlorine, which bed contains in excess of percent by weight of titanium dioxide and about 10 to 55 percent by weight of zirconium oxide, based on the mineral content of the bed, providing in the bed sufficient amount of carbonaceous material to ensure formation and vaporization of titanium tetrachloride from the bed and periodically feeding particles containing titanium dioxide and zircon to said bed, and continuing chlorination of said bed until the zirconium oxide concentration increases toward said 55 percent by Weight and in response to said increase of zirconium oxide concentration, allowing the temperature or" the bed to rise above 925 C. substantially from the heat generated from the formation of titanium tetrachloride to form and vaporize zirconium tetrachloride from the bed and maintaining the zirconium oxide content of the bed at said 10 to 55 percent by weight.

3. A method of producing titanium tetrachloride by exothermic chlorination of a fiuid bed containing titanium dioxide-bearing and zircon-bearing particles, which comprises establishing said fluid bed at 700 to 925 C. in a rising continuous stream comprising chlorine, which bed contains in excess of 15 percent by weight of titanium dioxide and about 10 to 55 percent by weight of zirconium oxide, based on the mineral content of the bed, providing in the bed sufiicient amount of carbonaceous material to ensure formation and vaporization of titanium tetrachloride from the bed and periodically feeding particles containing titanium dioxide and zircon to said bed, and continuing said chlorination until the titanium dioxide concentration of said bed falls toward said 15 percent by weight and the zircon concentration in the bed increases, and in response to said reduction of titanium dioxide and increase in zircon concentration in the bed, allowing the temperature of the bed to rise above 925 C. substantially from the heat generated from the formation of titanium tetrachloride to form and vaporize zirconium tetrachloride from the bed and providing sufficient titanium dioxide in the bed to maintain the titanium dioxide in the bed in excess of 15 percent by weight.

4. A method of producing titanium tetrachloride by exothermic chlorination of a fluid bed containing titanium dioxide-bearing and zircon-bearing particles which cornprises establishing said bed with a depth of at least one foot measured when the bed is static at 700 to 925 C. in a rising continuous gaseous stream comprising chlorine, which bed contains in excess of 15 percent by weight of titanium dioxide and about 10 to percent by weight of zirconium oxide, based on the mineral content of the bed, providing in the bed sufiicient amount of carbonaceous material to ensure formation and vaporization from the bed of titanium tetrachloride and periodically feeding particles containing titanium dioxide and zircon to said bed, and continuing chlorination until the bed increases in depth and the zircon concentration therein increases and concurrent therewith the titanium dioxide content in the bed decreases toward said 15 percent by weight and in response to the increase in depth and zircon concentration with concurrent decrease in titanium dioxide concentration, removing a portion of the bed and feeding an amount of titanium dioxide to the bed sutiicient to main tain the depth of the bed at least one foot and maintain a titanium dioxide content there in excess of 15 percent by weight, and on further chlorination of said bed provide an amount of zirconium oxide in said bed of about said 10 to 55 percent by weight.

5. A method of producing titanium tetrachloride by exothermic chlorination of a fluid bed containing titanium dioxide-bearing and zircon-bearing particles, which comprises establishing said fiuid bed with a depth of at least one foot measured when the bed is static at 700 to 925 C. in a rising continuous gaseous stream comprising chlorine, which bed contains in excess of 15 percent by weight of titanium dioxide and about 10 to 55 percent by weight of zirconium oxide, based on the mineral content of the bed, providing in the bed sutficient amount of carbonaceous material to ensure the formation and vaporization of titanium tetrachloride from the bed and periodically feeding particles containing titanium dioxide and zircon to said bed, and continuing chlorination of said bed until the depth thereof increases concurrent with an increase in the zircon concentration therein and a decrease in the titanium dioxide content toward said 15 percent by weight, and in response thereto, allowing the temperature of the bed to rise above 925 C., substantially from the heat generated from the formation of titanium tetrachloride to form and vaporize zirconium tetrachloride from the bed.

References Cited in the file of this patent UNiTED STATES PATENTS 1,209,258 Bradley Dec. 19, 1916 2,036,221 Kinzie Apr. 7, 1936 2,204,454 Teichmann et a1. Jan. 11, 1940 2,401,544 Brallier Jan. 4, 1946 2,425,504 Belchetz Aug. 12, 1947 2,701,179 McKinney Feb. 1, 1955 2,855,273 Evans et al Oct. 7, 1958 OTHER REFERENCES Barksdale: Titanium page 33 (1949), Ronald Press, New York, New York.

Fiat Final Report 774, Anhydrous Chlorides Manuf, pages 1819, May 7, 1946. 

1. A METHOD OF PRODUCING TITANIUM TETRACHLORIDE BY EXOTHERMIC CHLORINATION OF TITANIUM-BEARING MATERIAL CONTAINING TITANIUM DIOXIDE, WHICH COMPRISES ESTABLISHING A FLUID BED OF PARTICLES CONTAINING TITANIUM DIOXIDE AND ZIRCON AT 700 TO 925*C. IN A RISING CONTINUOUS GASEOUS STREAM COMPRISING CHLORINE, WHICH BED CONTAINS IN EXCESS OF 15 PERCENT BY WEIGHT OF TITANIUM DIOXIDE AND ABOUT 10 TO 55 PERCENT BY WEIGHT OF ZIRCONIUM OXIDE, BASED ON THE MINERAL CONTENT OF THE BED, PROVIDING IN THE BED SUFFICIENT AMOUNT OF CARBONACEOUS MATERIAL TO ENSURE FORMATION AND VAPORIZATION OF TITANIUM TETRACHLORIDE FROM THE BED AND PERIODICALLY FEEDING PARTICLES CONTAINING TITANIUM DIOXIDE AND ZIRCON TO SAID BED AND CONTINUING SAID CHLORINATION UNTIL THE TITANIUM DIOXIDE CONTENT REDUCES TOWARD SAID 15 PERCENT BY WEIGHT AND IN RESPONSE TO SAID REDUCTION IN TITANIUM DIOXIDE CONTENT, FEEDING ENOUGH OF SAID TITANIUM DIOXIDE MATERIAL TO THE BED TO PREVENT THE AMOUNT OF TITANIUM DIOXIDE IN SAID BED FROM FALLING BELOW SAID 15 PERCENT BY WIEGHT AND CONTINUING CHLORINATION TO ESTABLISH A ZIRCONIUM OXIDE CONCENTRATION OF ABOUT SAID 10 TO 55 PERCENT BY WEIGHT. 